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How do I clone a Django model instance object and save it to the database?
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Just change the primary key of your object and run save().
obj = Foo.objects.get(pk=<some_existing_pk>)
obj.pk = None
obj.save()
If you want auto-generated key, set the new key to None.
More on UPDATE/INSERT here.
Official docs on copying model instances: h...
How to set up Spark on Windows?
... http://spark.apache.org/docs/latest/building-spark.html
Download and install Maven, and set MAVEN_OPTS to the value specified in the guide.
But if you're just playing around with Spark, and don't actually need it to run on Windows for any other reason that your own machine is running Windows, I'd...
Data binding to SelectedItem in a WPF Treeview
...selects an item (aka OneWayToSource)?
– Shimmy Weitzhandler
Nov 21 '17 at 21:23
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Reverse / invert a dictionary mapping
...g aspect of this new implementation is considered an implementation detail and should not be relied upon. There is no guarantee it will stay that way so don't write code relying on Dict having the same behavior as OrderedDict.
– Mattias
Aug 26 '18 at 17:44
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Is it possible to set private property via reflection?
...lic, you apparently don't need to use BindingFlags.NonPublic to find it. Calling SetValue despite the the setter having less accessibility still does what you expect.
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单页web应用（SPA）的简单介绍 - 更多技术 - 清泛网 - 专注C/C++及内核技术
... main.innerHTML=data;
}
});
}
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参考原文链接：http://www.cnblogs.com/constantince/p/5586851.html
单页应用 SPA
How to print out more than 20 items (documents) in MongoDB's shell?
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From the shell if you want to show all results you could do db.collection.find().toArray() to get all results without it.
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Are Swift variables atomic?
... you, i.e.:
class Car {
static let sharedCar: Car = Car() // will be called inside of dispatch_once
}
private let sharedCar: Car2 = Car2() // same here
class Car2 {
}
Update 05/25/16: Keep an eye out for swift evolution proposal https://github.com/apple/swift-evolution/blob/master/proposals...
Is there a standard sign function (signum, sgn) in C/C++?
...T val) {
return (T(0) < val) - (val < T(0));
}
Benefits:
Actually implements signum (-1, 0, or 1). Implementations here using copysign only return -1 or 1, which is not signum. Also, some implementations here are returning a float (or T) rather than an int, which seems wasteful.
Works ...
IntelliJ gives Fatal Error: Unable to find package java.lang in classpath or bootclasspath
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Somehow the JDK language jars were removed from the classpath. All I had to do was reapply the JSDK home path.
Goto:
File -> Project Structure -> Platform Settings -> SDKs
Re-apply the JSDK home path.
Doing this added about 15 jars to the classpath. Apparently these are impo...